Principal Software Engineer, Radiant Nuclear

• The ideal candidate is patient, organized, and comfortable managing high volumes of cross-disciplinary requests, capable of diving deep into complex legacy stacks and synthesizing findings
• Bachelor's degree in Computer Science, Engineering, Physics or a related technical field
• 8+ years of professional experience in HPC, scientific computing, infrastructure, or platform engineering
• Deep Linux and sysadmin fluency, file systems, process management, and networking, with a hard-science approach to problem-solving
• Hands-on experience with HPC environments, simulation workloads, or academic/research computing (SLURM, PBS, MPI, Lustre, EFS, AWS ParallelCluster, or similar)
• Strong proficiency in one or more languages: Python, Golang, Rust, C#, or C/C++
• Strong code review skills, including the ability to read stack traces and chase down dense rabbit holes in high-compliance, legacy scientific software environments
• Exceptional communication skills; organized and effective when fielding a high volume of questions and requests from engineering stakeholders
• Ability to dive deep into complex, nested legacy stacks and then zoom out to synthesize findings clearly for a broader technical audience
• Must be willing to work extended hours and weekends as necessary to accomplish our mission
• Must work 100% onsite at El Segundo HQ

Desirable

• Radiant is seeking a driven Principal Software Engineer to own on-site High-Performance Compute infrastructure, scientific computing environments, and automation projects in tight collaboration with hard-science users and cloud infrastructure engineers
• You will work closely with the software team to design scalable, secure, and resilient compute practices, tools, and systems across the entire organization
• As a technical lead, you will define team scope, shape individual responsibilities, and serve as the primary liaison between engineering and software teams, acting as the subject-matter expert on HPC workflows, simulation tooling, and compute optimization
• The infrastructure you manage, the pipelines you build, and the developer-productivity culture you establish will help you design, run, and mass-produce the first high-temperature gas-cooled portable microreactor ever to be commercialized
• Lead HPC initiatives as driven by the software org, establishing responsibilities, project scope, and technical mentorship
• Own workflows, tooling, and performance for scientific computing, including Ansys, STAR-CCM+, and Abaqus, covering licensing, environment setup, job orchestration, and results infrastructure
• Dive deep into HPC software, workload scheduling, data movement, storage hierarchies, and compute environments to build robust, high-throughput Linux systems
• Serve as the go-between for engineering teams and software, fielding HPC questions, simulation software issues, and infrastructure needs from nuclear, thermal, materials, mechanical, and electrical engineers, translating them into actionable work
• Triage inbound infrastructure requests, HPC/MPI/Linux debugging, job failure analysis, and shell and systems mentorship, while prioritizing effectively and communicating clearly across stakeholders
• Modernize legacy scientific computing systems and tooling, migrating to current stacks to improve maintainability, performance, and developer experience
• Design and maintain networking infrastructure for distributed simulation systems, optimizing data transfer between HPC clusters
• Partner with DevOps engineers to architect and maintain systems across AWS and on-premises Linux environments, ensuring high availability, security, and performance for mission-critical workloads
• Architect tools supporting build systems, testing frameworks, deployment automation, and developer environments